Software-Defined Networking (SDN) is an evolving networking paradigm. A logical overlay network that is implemented over a physical network infrastructure (e.g., of an enterprise datacenter or a hosting system) is a good example of SDN. A logical network, logically connects different virtual machines (e.g., of a tenant of a hosting system), which run on one or more host machines, to each other and to other external networks (i.e., other physical and/or logical networks). Between the virtual machines (VMs) of a common host, network data is transmitted within the host machine (i.e., does not pass through physical cables and switches that connect the host machines). This type of traffic is called intrahost network traffic. On the other hand, the network traffic communicated between VMs of different hosts, which is called interhost traffic, is transmitted through at least some of the physical switches and cables of the physical network. Since intrahost traffic uses only the computing sources of a host machine (and not the physical network), intrahost traffic is highly preferable over interhost traffic in datacenters and hosting systems.
Additionally, a widespread VM placement within a hosting system (e.g., VMs that implement a particular application) increases the probability of co-residence threats (i.e., when an attacker VM and a victim VM operate on the same host machine). In order to reduce interhost traffic, high-end switches with large bandwidth capacities that can generate a high volume of interhost bandwidth have been introduced to the market. However, these high-end switches are not cost-effective. Moreover, using high-end switches limits the throughput of computing tasks in datacenters.